Today I got a 4GB CF that was advertised as being 150x speed, which means I should be able to transfer data to it at up to about 22MB/s. I have an internal, USB2 multicard reader for my PC and when copying a large file onto it under KDE I wasn't getting more than 4MB/s

Could it be that my card reader doesn't support the CFII/III transfer modes or is it just that I've been lied to about the speed of the card?

The 150x speed is usually the read speed. The 150x speed is also usually the test read speed obtained from a large block of file whose size is the optimal for read transfer for this CF.

eg, If you are reading 1024 x 1KB size files vs read 1 x 1MB file, the 1MB file will be read or written much faster.

Further, write speed is usually lower and the card reader do play a part.

Also be aware when you move it to the Zaurus that the bus is a bottleneck on the Zaurus since it is also used for memory too.

Take at this posting for some comparative figures between Microdrive and SanDisk Extreme III http://www.oesf.org/forums/index.php?showtopic=19602, note that further on into the post it shows the significant ramp up in performance associated with some overclocking.

-Andy